Geometric optics


The physical is a very broad science that includes different types of sciences. One of these is the geometric optimum , a branch that is responsible for conducting studies and analysis using the different simple geometric laws that already exist on the types of changes that occur in the direction experienced by the rays of light when the processes occur. refraction and reflection.


What is geometric optics?

The geometrical optics is a science that conducts studies on how the light rays can move , in other words, studies the direction they take when presented reflection or refraction of light.

  • Definition of geometric optics
  • What studies
  • Applications
  • Characteristics of geometric optics
  • Laws
  • Formulas
  • Experiments
  • Instruments
  • Importance of geometric optics
  • Examples
  • Books

Definition of geometric optics

Geometric optics is a science that is based above all on several fundamental principles from which it is possible to understand how optical instruments used in daily life, such as vision lenses, cameras, mirrors behave. and even the organ of sight, the eye. It studies all the images that are generated thanks to the processes of reflection and refraction of light and among its main functions are to analyze the path of light rays, their wave movements and interferences.


What studies

This science is responsible for studying the nature of light itself. In addition, it conducts research and analysis on the laws that govern all the light effects that exist as well as the way in which light can come to relate and interact with a certain substance.


There are several areas in which geometric optics can be applied, these are:

Optical instrumentation

This field includes everything related to the study and the design of the systems that are used to collect images , for example, lenses, prisms, microscopes, telescopes.


In the area of ​​communication it is used as a means of carrying information and optical systems participate directly in the transmission and reception of signals. It can be used in detectors, laser lights, signal processing, and holography. Perhaps one of the most important applications in this regard is fiber optics because it is thanks to it that it is possible to have and use the internet.

Optical metrology

In this field it is used to monitor the different physical parameters that exist and the methods to measure using only light. It is common to see it in the processing of images, in the emission of light and in the different optical systems .

Frontier optics

This term refers to research carried out with respect to high power light radiation . It also helps to quickly detect information and at the same time transmit it through optical materials, radiation sources and light detection.

Characteristics of geometric optics

One of its main characteristics is that it has an object, in this case it will be the source from which the rays originate and it can be through its own light or when it is reflected . The objects of geometric optics are point or non-point . It also has a diopter which is the surface that is responsible for separating the media that have different refractive index. It uses a series of geometric representations to express changes in the direction of light rays and also depends on the phenomena of reflection and refraction .


The laws of geometric optics are as follows:

Rectilinear propagation of light

This law tells us that light rays always propagate as a straight line and that they also have the same speed in all directions. For this law to be fulfilled, it is necessary that the dimensions of the objects are greater than the wavelength of the light so that the formation of diffraction is avoided and that the propagation medium is homogeneous.

Ray independence

He explains that each ray is independent from the others and that for this reason they do not interfere with each other.

Reflection and refraction

These are also two laws that are used to be able to foresee the possible changes that occur in the direction that the rays take.


It is also known as the reciprocity law and establishes that the path of a ray that leaves A to reach B by means of a reflection is the same as that of a ray that starts in the opposite direction and is reflected .


As for the formulas there are many of them, below we mention some of the most important.

  • icroscopio : A = ALobj⋅Aaoc = -df’obj⋅xpf’oc
  • Telescope : Aa = αfαi = −f’objf’oc
  • The Photographic Camera : E. = log2 (N2t) = 3.32⋅log (N2t)
  • The Human Eye : 1s’ − 1s = 1f ‘= – 1f
  • Flat mirror : s’ = – s
  • Diopter plan o: n’s’ = ns


One experiment that can be done to check geometric optics is by using a cell phone as a type of source to reproduce holograms . You can also create a homemade spectrometer whose objective is to be able to project the colors of the rainbow in a striking way to demonstrate the importance of light in different physical phenomena, showing at the same time the refraction and reflection of light .


Some commonly used instruments that use the principle of geometric optimum are the following:

  • Telescope : instrument that allows the observation of objects that are at great distances with better detail since it captures the electromagnetic radiation of light.
  • Microscope : through geometric optics you can see tiny objects that could not be seen with the naked eye.
  • Magnifying glass : consists of a converging lens that helps to obtain a broader view on a small object.

Importance of geometric optics

One of the most important aspects is that the human eye is formed by a geometric optical system and thanks to it, it is possible to create an image of an object on the internal surface found in the eye. Another important aspect of this science is its use in technology because thanks to this, communication and even many diagnostic means are now possible to manufacture with more precision. It is a science that also participates in various aspects of daily life such as scientific research and military applications .


Geometric optics can and is used as a type of basic tool for the design of optical systems, whether or not they produce images. It can be seen in the construction of glasses , contact lenses , cameras , microscopes , telescopes and in many products related to television and film production . In addition, it is responsible for providing the possibility of enjoying a wide network to make it possible for internet and modern telephony signals to be available practically all over the world.


Some important books that explain geometric optics are:

  • Bruno Rossi Optics Fundamentals
  • Geometric optics by Lilia Colonato Courrol and André Oliveira Preto
  • Geometric optics: theory and questions of Hernández, Domenech, Vázquez and Illueca
  • Geometric and radiometric optics practices by Pascual Villalobos, Hernández Poveda, Fimia Gil and Mateos Álvarez

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